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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
var fib = function(N) {
    if( N==0 ){
        return 0
    }
    else if( N==1 ){
        return 1
    }
    return fib(N-1) + fib(N-2)
};

var N = 4
console.log(fib(N))
    </script>
</body>
</html>